This image of comet Wild 2 shows one hemisphere in sunlight and the other in shadow, like a view of the quarter Moon. Several large depressed regions can be seen. The comet is about 3.1 miles (5 kilometers) in diameter.(Image credit: NASA/JPL/Stardust)
Andrea Thompson is an associate editor at Scientific American, where she covers sustainability, energy and the environment. Prior to that, she was a senior writer covering climate science at Climate Central and a reporter and editor at Live Science, where she primarily covered Earth science and the environment. She holds a graduate degree in science health and environmental reporting from New York University, as well as a bachelor of science and and masters of science in atmospheric chemistry from the Georgia Institute of Technology.